'The Big Bang Theory' cast then and now

It's hard to believe it's been eight years since "The Big Bang Theory" hit the small screen on Sep. 24, 2007! With the ninth season premiering earlier this week, as well as star Kaley Cuoco's shocking split from Ryan Sweeting -- we're reminiscing about the beginning of everyone's favorite CBS sitcom. Click through to take a look at how much the stars have changed from their first days on the show, then find out what they're up to now!

It's hard to believe it's been eight years since "The Big Bang Theory" hit the small screen on Sep. 24, 2007! With the ninth season premiering earlier this week, as well as star Kaley Cuoco's shocking split from Ryan Sweeting -- we're reminiscing about the beginning of everyone's favorite CBS sitcom. Click through to take a look at how much the stars have changed from their first days on the show, then find out what they're up to now!